Fostex’s RP series of headphones has decades worth of legacy in the audio production world. Their “regular phase” planar magnetic driver is one of the earliest examples of the technology. Planar magnetic drivers use a thin energized membrane suspended between magnets instead of a traditional dynamic speaker cone assembly, with the goal of reducing distortion and improving overall audio fidelity. The Fostex RP driver features some of the good characteristics of newer planar drivers packed into a solid frame, but its far less suited to multi-purpose listening than other popular studio headphones.
The most recent Mark 3 update of this headphone launched about six years ago, and subtly refined the headband design and audio tuning while keeping the core driver intact. It’s available in three models: T20RP, T40RP, and T50RP, and each one has a street price of around $160, which is what I paid on Amazon. That price makes these slightly cheaper than the average planar headphone. You can check out their official product page right here, and that’s not an affiliate link as I think those have no place in reviews.
Each model uses the same driver, the same overall build, and features the same two cables: a 3m cable with a 6.3mm plug, and a 1.2m “mobile” cable that’s bright orange and has a 3.5mm connector. The 20RP is a fully open model with the loudest bass response. The 50RP is semi-open, with a brighter, more neutral sound. And the 40RP that I bought is closed, with “focused bass.” More on what that means in a moment.
The differences in openness come from different materials placed in front of a small vent on the lower part of the ear cups. These headphones are user-serviceable, and this vent is easy to access, so if you’re confident enough you could modify any of them yourself to mimic the different tunings of each model.
Unfortunately, this is one of the most uninspiring headphones I’ve listened to in a while. Its signature makes some sense for a studio monitoring/tracking environment, where you need rugged cans for recording vocal tracks…but in a home listening environment these might not be ideal. The “focused” bass of the 40 model amounts to some gentle emphasis in the higher bass, and sub bass that’s rolled off into oblivion.
There’s very little in the way of proper sub or mid bass rumble, and any bass that does show up is gentle and lacking resonance or character. It’s not totally missing, and not unpleasant, but it just doesn’t have anything going for it. This is a bit of a bummer, because planar drivers are normally great at producing powerful, accurate bass. The driver here is likely up to the task, but from what I understand all three stock RP models have sub bass issues, so maybe this older design isn’t doing it any favors.
The high bass emphasis also bleeds into the midrange, giving the mids a hint of a dark texture. It’s not quite muffled or bad, but it does make vocals sound creamier and more bass-heavy than they do in reality. This issue is further compounded by upper mids that lack any energy or zing. Most of the information in music lives in the midrange, and although the slightly dark texture here makes music pleasant to listen to for long sessions, it’s not really that accurate to your input source compared to other headphones in this price range.
This could have been salvaged with some treble excitement, but the treble is a bit relaxed and withdrawn just like the bass. It doesn’t have any of the harsh peaky sibilant energy of other popular studio pairs like the 7506 or DT770. Like the bass it’s just sort of…present. And like the bass, it’s subdued enough to make these one step below what I’d call accurate.
On top of all that, the headphones aren’t that sensitive, so I’d recommend a dedicated amplifier. They’re rated at a mere 91dB of sensitivity per milliwatt when most modern studio pairs are closer to the 100dB range. I think that rating is a little lower than the true volume, as I was able to achieve a listenable volume at maximum power out of the dreaded PS4 controller, but you’ll want an amp for these to sound their best.
Nothing about the sound is bad but it’s all a bit bland and lackluster. The AKG K361/K371 both offer vastly superior sound reproduction for a similar price, and with a high sensitivity that doesn’t require extra audio hardware. The DT770 offers more excitement in the treble and the bass. All of those also do a better job of straddling the line between the studio production world and home listening. As far as older studio designs go, I also prefer the sound of both the Beyerdynamic DT150 and 250.
In spite of all that nitpicking, there’s just enough to enjoy about the sound that I’ve still had a good time listening to the T40RP’s over the last week. Imaging is pleasantly precise and okay for gaming in spite of the relaxed mids, though the closed back design and intimate pads mean width and air are both lacking compared to the competition.
The sound issues be easier to accept if the rest of the headphone delivered perfection, but unfortunately the comfort also isn’t up to modern standards. The headband padding and adjustability, via two metal sliders that stay in place with friction, are both fine. There’s plenty of swivel in the cups and enough adjustment range that these should fit on almost any head. I have a ton of extra adjustment room even on my big head.
The big problem is the ear pads. They use a hybrid on-ear/over-ear design, similar to Sony’s V6 and 7506 models. Unfortunately, they just don’t do it all that well. The hole in the center is barely big enough to fit around your ear, but so shallow that the entire inside of the enclosure sits smashed against your ear. It has some foam inside surrounding the diagonally-mounted driver, but it’s very hard, and after around an hour pressed against my ears it starts to feel bad and I have to take a break.
It could have been saved by the large pancake-shaped padding around the hole, but it’s not thick enough. It’s a shame, because that exterior padding is rather nice and plush, but about half as thick as it should be to ensure long-term comfort. It’s much wider than the 7506 padding, and as such does a good job of sealing on my head even while wearing glasses. But isolation is merely average, and again, the thin padding starts to press against my head in unpleasant ways after an hour or two.
Many reviewers recommend changing the pads, but I like to review headphones in their stock configuration. And if you’re a costumer paying $160 for headphones, they should have functional pads and shouldn’t require pain breaks every hour. Hobbyists have changed the pads on these for years, and the Mark 3 revision was Fostex’s chance to fix this long-held complaint.
Instead, they didn’t.
The rest of the build and design are exceptional. The frame is made of durable metal and plastic components, and has that true tank-like feel that all studio gear should have. I have no fears about long-term durability. The frame is sleeker than I expected, and doesn’t stick out far from my head. The shock orange braided cables that connect the ear cups together and the bright Fostex branding on the headband both remind me of typical gaming headset flair. This is a little strange in what’s otherwise an understated-looking pair of studio headphones.
Both of the cables lock into place in a deeply- recessed connector hole, so finding replacements might be slightly difficult. The two included cables are nice and supple, and I have no complaints about their quality.
The Fostex RP series is still one of the most affordable planar magnetic headphone families on the market. If you’re curious about this driver technology, or you’re looking to get into the hobbyist world of modifying headphones, they might be worth a look. If you’re looking for a purpose-built studio monitoring headphone, these still have the right type of sound and build to fit perfectly into that task.
However, if you want a studio headphone that can also do double-duty as a home listening pair, there are so many other better options at this same price that don’t require you to replace the pads for maximum comfort. The T40RP is a fun curiosity for my personal collection, but it’s a bit past its prime compared to the rest of the market. It’s simply not comfortable or performant enough to compete with other newer oft-recommended pairs without costly modification.
I’m happy to have one of these in my collection in spite of their many flaws. I love the awesome build quality and the unique sound of the drivers. I had just as much fun touching and adjusting these over the last week as I did listening to them, which I think says a lot. They’re a great early take on planar magnetic tech, but they shouldn’t be on the short list for most listeners.